Before releasing Matomo 5 we will soon switch the base branch from
5.x-dev. Some of our actions are automatically running on the base branch. For this purpose we need to update the used branch for some actions.
Should be safe to already merge this, as the changes here should first be used when the base branch was changed.
But it should meanwhile already be possible to trigger the actions manually for
5.x-dev after this was merged.
Updating the action to use that stuff will require some more testing I guess. I would say that's out of scope for this PR, as it should only prepare some stuff for Matomo 5. We should maybe create an issue to update that stuff somewhen else.